We propose to refine, implement, evaluate, enhance, and generalize a suite of software services intended to interface well-formed terminologies with arbitrary applications. This suite of services will be available in an open source mode, coordinated by a consortium. Our goal will be achieved by the following Specific Aims: Integrate existing service specifications into one practical, implementable, and modular interface specification; using the open-source development model, create a reference implementation of the integrated terminology services specification; utilize these products to analyze different approaches to federated term lookup and post-lookup composition; expand the specification and relevant implementations to accommodate domain context dependencies and user-specific profiles; and deploy variations of implemented terminologies services components into EMR client applications and evaluate behaviors in a formal usability lab context.